1. Field of Application
The present invention relates to semiconductor light-emitting devices such as semiconductor lasers, light-emitting diodes, etc, and in particular relates to semiconductor light-emitting devices having emission wavelengths in a range which includes the blue to ultra-violet region of the spectrum.
2. Prior Art Technology
In recent years semiconductor lasers have been realized in practice, which utilize AlGaAs/GaAs III-V semiconductor materials. When a semiconductor laser is used in a data processing application such as data readout from an optical disc, or in a laser printer, it is desirable that the emission wavelength of the light produced from the semiconductor laser be as short as possible, in order to maximize the data processing performance. However with semiconductor lasers that have been utilized hitherto, even if the activation layer of the laser is formed of a material such as AlGaInP, which has a large size of forbidden energy gap and is among the direct-transition type III-V semiconductor materials, it is only possible to achieve an emission wavelength that is in the range 580 to 690 nm. Thus, the emission wavelength cannot be made sufficiently short to reach the blue region of the visible spectrum. Another direct-transition type compound semiconductor material which has an even larger value of forbidden energy gap is Zn(SSe), which is a II-VI compound semiconductor. However due to the difficulty encountered in controlling p-type conduction in this material, it has not been possible to utilize it to obtain emission in the blue to ultra-violet region of the spectrum.
A similar problem arises with light-emitting diodes. Red light-emitting diodes (LEDs) which employ AlGaAs and green LEDs utilizing GaP are now widely utilized as display devices. However there is a need for a capability for practical manufacture of blue-emission LEDs, in order to increase the number of colors which can be used in such display applications. This has not been possible up to the present.